Look through our GeoStory “Public Transportation,” which provides maps for buses, trains, and metros. (Maps are not included for ferries, another popular mass-transit option.) Which maps are your favorites? Which do you think were difficult to design?

Maps for public transportation systems serving large urban areas are probably more difficult to design, because they must include numerous stops or stations, incorporate familiar landmarks, and be usable for both everyday commuters (who know the area) and tourists (who don’t). Sydney, London, Hong Kong, Santiago, and Tehran have huge public transportation systems.

Maps for an older, well-established public transportation system are probably more difficult to design, because they must balance what commuters are familiar with and what is new and updated. London and Moscow metro systems are well-established and constantly updated.

Watch our terrific media spotlight video, “Selecting a Map Projection.” In it, the cartographers at National Geographic explain that every map is a little bit (or a lot!) distorted, and how mapmakers must choose what features to prioritize when choosing a map or map projection. According to the video, why did Nat Geo cartographers use the “interrupted Mollwide” projection for their September 2012 map supplement—what features were prioritized? When would this map not be useful?

Nat Geo cartographers used the interrupted Mollwide because it accurately compares area. The display of the ocean was prioritized in this map, so cartographers chose a projection centered on the Pacific. This projection shows all three oceans in their entirety, with the least distortion possible.

An interrupted Mollwide projection would not be useful for navigation purposes, because angles and shapes are not prioritized. The Mercator projection, also shown in the video, preserves angles and meridians. This makes it more useful for oceangoing navigation.